The White Heelsplitter (Lasmigona complanata) is a large mussel with a sharp projection (wing) on the top of its shell above the hinge. It was widespread in the Illinois River in the early 1900s, but today lives only in the lower half of the valley because of pollution upstream. The white heelsplitter was not considered a good button species because usually only the anterior one-third of the shell was thick enough to make buttons. (Conservation Status: Currently Stable)